FLOOR and ROUND( <cellreference> , 0) will have different behavior for negative numbers.

ROUND(-27.3, 0) will give you -27. But the highest integer that's less than -27.3 will be -28.

For positive numbers, FLOOR is also only going to provide you with the nearest integer if the portion after the decimal place is less than 0.5; otherwise ROUND ( <cellreference>, 0) will be better to use if you want the nearest integer in all situations.

TRUNC just gets rid of everything after the decimal place; but again, for positive numbers, that won't give you the closest integer all the time, only for numbers where the non-integer part is less than 0.5.

Click cell B1 , type TRUNC(, then click cell A1, add a ) and press enter. This should put the correct number in B2, which you can then drag the corner of to cell B100 to fill every cell with the proper formula.